1. Field of the Invention
The present invention relates to pulper and method for comminuting and suspending paper stock.
2. Description of the Related Art
Pulpers of this type are mainly used to put air-dry pulp material or waste paper into suspension. The material put in large pieces, webs or compressed bales is mixed intensively with water, for which purpose a mixing and comminuting rotor is generally used. A pulper substantially comprises a container for the suspension and the rotor previously mentioned. In many cases, it also contains a screen in the bottom region, through which the suspension can be pumped away.
Understandably, such pulpers are optimized continually, the aim essentially being pulping that is quick and economical in terms of power. As a standard type for a pulper, a cylindrical container standing upright having a rotor in the bottom region has become widespread. In this container, water and stock to be pulped are added from above and, with the aid of the rotor, a funnel flow is produced in the suspension, in which, therefore, in the central region, the stock is sucked downwards by the rotor and is forced radially outwards in the bottom region, which results in a circulatory flow. Flow measures are also known in order to control this circulatory flow. For example, by means of appropriate internal flow fittings (flow breakers) on the container wall, the peripheral flow is braked, since this flow furnishes only a small contribution to the pulping. On the other hand, the promotion of the actual circulation, that is to say the repeated transport of the stock to be pulped into the rotor region, provides an improvement to the effect.
Attempts are also made to incorporate the stock freshly put into the suspension as quickly as possible. For these reasons, much development has been carried out on the rotors and containers of the pulpers.
In DE 196 01 497 A1 it has been proposed to configure the container of the pulper to be angular, in order to improve the entrainment of the stock. A further improvement should be effected by the asymmetrical arrangement of the rotor. However, these pulpers have not been widely employed.
Another attempt to improve pulpers of this type is shown by DE 36 38 993 C2. According to this text, the flow of the suspension is produced with the aid of a rotor fitted laterally. The oblique positioning of the rotor axis has already been carried out, e.g. in a pulper shown by DE 32 34 702 C2, in which a rotor fitted relatively high assumes an acute angle with respect to the vertical.
In order to improve the circulation, unconventional paths have also been followed, such as, according to DE 34 29 514 C2, a plurality of complicated rotors within the saure pulper container.
What is needed in the art is a more efficient pulper, without substantial additional expenditure, improving the entrainment of the material.